Organic Farming Enhances Diversity and Recruits Beneficial Soil Fungal Groups in Traditional Banana Plantations

Abstract

This study investigates the impact of organic (OF) and conventional farming (CF) on soil fungal communities in banana monoculture plantations on Madeira Island. We hypothesized that OF promotes beneficial fungal groups over harmful ones, sustaining soil health. Soil samples were collected from six plantations (three OF and three CF) for ITS amplicon sequencing to assess fungal diversity. Results showed that OF significantly enhanced fungal alpha-diversity (Shannon-Wiener index) and Evenness. The phylum Ascomycota dominated OF systems, while Basidiomycota prevailed in CF. Mortierella, a beneficial genus, was abundant in OF and is observed in CF but was less evident, being the genus Trechispora the most well represented in CF agrosystems. Additionally, OF was associated with higher soil pH and Mg levels, which correlated positively with beneficial fungal groups. Functional analysis revealed that OF promoted saprotrophic fungi, crucial for the decomposition of organic matter and nutrient cycling. However, both systems exhibited low levels of arbuscular mycorrhizal fungi, likely due to high phosphorus levels. These findings suggest that organic practices can enhance soil fungal diversity and health, although attention to nutrient management is critical to further improving soil-plant-fungi interactions.

Keywords: banana soil fungi; functional groups; fungal diversity; mycobiome; organic farming.

Figure 1

Variation of α-diversity indices in both management systems, conventional farming (CF) and organic farming (OF). The significant difference between CF and OF is labeled with (*), Mann–Whitney U test, p < 0.05. (A) Species Richness, (B) Shannon–Wiener, (C) Evenness.

Figure 2

Mean relative abundance of phyla in (A) each banana agrosystem and (B) each management system.

Figure 3

Mean relative abundance of genera in (A) each banana agrosystem and (B) each management system. Graphics discriminate the top 25 genera.

Figure 4

Observed Spearman’s correlations between the top 25 genera (+Fusarium) and pH, Mg, and Ca. Size of circles: the larger the circle, the smaller the p-value.

Figure 5

Variation of the abundance of fungal functional groups in each management system, conventional farming (CF) and organic farming (OF). The significant difference between CF and OF is labeled with * p > 0.05 or ** p > 0.01, Student’s t-test (p < 0.05), Welch’s t-test (p < 0.05) or Mann–Whitney U test (p < 0.05), depending on if homogeneity of variance and normality of the data were verified or not.

Figure 6

CAP based on the Bray–Curtis dissimilarity distance matrix of soil fungal functional communities in two management systems, conventional farming (CF) and organic farming (OF), and the relation with soil physicochemical properties.